Inkjet and inkjet-based 3D printing:connecting fluid properties and

printing performanceYang Guo, Huseini S. Patanwala and Brice Bognet

Institute of Materials Science, University of Connecticut, Storrs, Connecticut, USA, andAnson W.K. Ma

Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, Connecticut, USA andDepartment of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, USA

AbstractPurpose – This paper aims to summarize the latest developments both in terms of theoretical understanding and experimental techniques relatedto inkjet fluids. The purpose is to provide practitioners a self-contained review of how the performance of inkjet and inkjet-based three-dimensional(3D) printing is fundamentally influenced by the properties of inkjet fluids.Design/methodology/approach – This paper is written for practitioners who may not be familiar with the underlying physics of inkjet printing.The paper thus begins with a brief review of basic concepts in inkjet fluid characterization and the relevant dimensionless groups. Then, how dropimpact and contact angle affect the footprint and resolution of inkjet printing is reviewed, especially onto powder and fabrics that are relevant to3D printing and flexible electronics applications. A future outlook is given at the end of this review paper.Findings – The jettability of Newtonian fluids is well-studied and has been generalized using a dimensionless Ohnesorge number. However, theinclusion of various functional materials may modify the ink fluid properties, leading to non-Newtonian behavior, such as shear thinning andelasticity. This paper discusses the current understanding of common inkjet fluids, such as particle suspensions, shear-thinning fluids and viscoelasticfluids.Originality/value – A number of excellent review papers on the applications of inkjet and inkjet-based 3D printing already exist. This paper focuseson highlighting the current scientific understanding and possible future directions.

Keywords Review, Rheology, 3D printing, Inkjet printing, Surface science

Paper type Literature review

1. IntroductionInkjet printing has been widely adopted, as the technology wasfirst developed in the 1960s to 1970s (Buehner et al., 1977;Elmqvist, 1951; Sweet, 1965, 1975; Vaught et al., 1984).Presently, inkjet printing has evolved from applications suchas product coding and graphic art printing to more advancedapplications such as digital fabrication and additivemanufacturing. As shown in Figure 1, the number of journalarticles published on inkjet printing has grown steadily sinceearly 2000s, with a lot of patent activities occurring between2004 and 2007. Inkjet printing has a number of technicaladvantages, making it an attractive method for manufacturing.First, inkjet printing is a non-contact method. It is scalableand is less susceptible to contamination and substrate or maskdamage. Second, inkjet printing is a digital process offeringgreat versatility in terms of patterning through dropdeposition. It has been applied to create three-dimensional(3D) structures layer-by-layer by printing a binder onto a

powder bed or jetting a photopolymer which is subsequentlycross-linked (Sachs et al., 1992; Wang et al., 2008). Third,inkjet printing is compatible with different fluids includingpolymer solutions, particle suspensions and biomoleculesprovided that the “ink” satisfies certain fluid requirements.Table I summarizes some common types of inkjet fluids andtheir applications.

1.1 Printing process overviewThe two main modes of inkjet printing are continuousinkjet (CIJ) mode and drop-on-demand (DOD) mode, asillustrated in Figure 2(a) and (b). In both methods, theliquid goes through an orifice or nozzle. In the CIJ mode, asits name suggests, the fluid is pushed through the nozzlecontinuously. The jet then breaks into a stream of dropletsas a result of capillary-driven Rayleigh-Plateau instability.Droplets are charged and deflected using field plates ontothe substrate during printing, while the rest are collected bya catcher for recycling. CIJ typically produces a high dropvelocity (!10 ms"1) (Derby, 2010) and thus enables fast

The current issue and full text archive of this journal is available onEmerald Insight at: www.emeraldinsight.com/1355-2546.htm

Rapid Prototyping Journal23/3 (2017) 562–576© Emerald Publishing Limited [ISSN 1355-2546][DOI 10.1108/RPJ-05-2016-0076]

The authors would like to acknowledge the Faculty Large Grant at theUniversity of Connecticut for financial support.

Received 5 May 2016Revised 21 June 2016Accepted 24 June 2016

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processing for applications such as marking and bar coding.Due to the continuous jetting action, the nozzle is less likelyto be clogged due to solvent evaporation especially if avolatile solvent is used. However, the resolution of CIJ isgenerally lower than that of DOD (Hutchings and Martin,2012). Also, the deposition of small fragmented drops ontothe field plates can modify the electric field and in worstcases can lead to printer failure. Recycling of the ink mayalso lead to contamination and require re-adjusting the inkconcentration to account for solvent evaporation.DOD-type inkjet printing is more widely used, where thedrop is only generated as needed by thermal or piezoelectricactuation. The typical drop velocity is around 5 to 8 m s"1

(Hutchings and Martin, 2012). A drawback of DODprinting is the drying of ink at the nozzle during downtime,which may further lead to particulate deposition at thenozzle and possible clogging.

Several 3D printing methods are based on inkjettechnology. For instance, in the 3DPTM powder-bed methodlicensed by MIT, a binder is printed onto a powder bed. Asillustrated in Figure 2(c), the binder material selectivelyconsolidates the powder, thereby forming a quasi-2D pattern.The fused layer is then lowered into the powder bed, andanother layer of powder is smoothly spread onto the surface bya roller, followed by another round of binder printing. Byrepeating this process, 3D structures can be fabricated (Sachset al., 1993). Such method has been applied to createceramic-based polymer composites (Seerden et al., 2001) andintricate candies (von Hasseln, 2013). More recently, one ofthe licensees, Aprecia Pharmaceuticals, has applied the3DPTM method to create FDA-approved fast-dissolvingtablets (Katstra et al., 2000; Rowe et al., 2000). Processdevelopment steps from powder and binder selection topost-processing for 3DPTM are reviewed by Utela et al.(2008). Another inkjet-based 3D printing method involvesprinting photopolymers and support materials layer-by-layer,where the water-soluble support material will be subsequentlyremoved.

1.2 Printing performance parametersRegardless of the method, the printing performance isevaluated in terms of the resolution, consistency and dropplacement accuracy. Dots per inch (DPI) is commonly used asa measure of printing resolution, which accounts for thedistance between two adjacent droplets deposited on thesubstrate, depending on the incremental X and Ydisplacements of the print head or substrate. However, theresolution also depends on the actual footprint of thedeposited drops, which is not specified in DPI. For DODinkjet printing, the spatial resolution is typically on the orderof tens of microns (Hutchings and Martin, 2012). Thefootprint of a drop further depends on the drop volume andthe contact angle between the drop and the substrate.

Figure 1 (a) Number of new journal articles published from 1973to 2015, data collected using Scopus with “inkjet” as the searchkeyword; (b) number of new patents from 1973 to 2015, datacollected using LexisNexis with “inkjet” as the search keyword

Table I Common materials and application examples of inkjet printing and inkjet-based 3D printing

Category Sample materials Application examples

Polymers, monomers and oligomers Conjugated polymers [e.g. poly(3,4-ethylenedioxythiophene), poly(pyrrole), polyaniline,and poly(p-phenylene vinylene)]

Transistors (Sirringhaus, Kawase et al., 2000),displays (Shimoda et al., 2003), polymerlight-emitting devices (PLED) (Bharathan andYang, 1998), sensors (Crowley et al., 2008;Dua et al., 2010), solar cells (Chen et al.,2009), 3D structures (van den Berg et al.,2007), radio-frequency identification (RFID)(Rida et al., 2009; Yang et al., 2007), andflexible electronics (Perelaer et al., 2006)

Metal and metal oxide, carbon materials Silver and gold nanoparticle dispersions; Silver andgold precursor solutions; Graphene, carbonnanotubes and carbon black

Ceramic Alumina, zinc oxide and silicon nitride/oxide Capacitors, 3D structures (Cappi et al., 2008;Seerden et al., 2001)

Biomaterials Biomolecules (e.g. proteins and DNA) and cells Biochips, biomarkers (Delaney et al., 2009;Okamoto et al., 2000), biosensors andimmunoassay tests (Delaney et al., 2009),and regenerative medicine (Calvert, 2007;Lorber et al., 2014; Murphy and Atala, 2014)

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Consistency is especially important for large-scalemanufacturing. Inconsistency due to misfiring, nozzle-plateflooding and satellite drop formation are closely related tothe fluid properties, namely, rheology and surface tension, ofthe ink. Drop placement error is defined as the differencebetween the target location and the impact location (Lean,2002). The error is influenced by the precision of the nozzlemanufacturing and the distance between the nozzle andsubstrate. In high throughput systems, the substrate moves ata high speed (e.g. Kodak Inkjet printer Versamark® Series cango up to 1,000 feet/min). Positioning smaller drops becomesincreasingly difficult as a boundary layer is developedimmediately above the surface of moving substrate, which maydeflect the drops and, in some cases, prevent the small dropsfrom reaching the substrate surface entirely (Leoni and Gila,2013).

1.3 Review scope and structureThis paper summarizes the latest developments both in termsof theoretical understanding and experimental techniquesrelated to inkjet fluids. This review paper is written withpractitioners in mind, who may not be familiar with theunderlying physics of inkjet printing. For this reason, thepaper starts with a brief review of basic concepts in inkjet fluidcharacterization and the relevant dimensionless groups fordescribing the inkjet printing process. To further connect theprinting performance with the fundamental understanding, wediscussed three types of commonly used inkjet fluids, namely,particle suspensions, shear-thinning fluids and viscoelastic

fluids. These inkjet fluids are “complex fluids” that possessmechanical properties that are intermediate between ordinaryliquids and ordinary solids” (Gelbart and Ben-Shaul, 1996;Larson, 1999). Additionally, we also review how drop impactand contact angle affect the footprint and resolution of inkjetprinting. Of particular interest are drop spreading andinfiltration for powder and fabrics that are technologicallyimportant for 3D printing and smart clothing. Finally, a futureoutlook is given at the end of this review paper, highlightingtechnological gaps and possible future research directions. Allin all, this paper aims to provide practitioners a self-containedreview without duplicating excellent existing reviews on thejetting of Newtonian fluids and inkjet printing (Derby, 2010;Eggers and Villermaux, 2008; Martin et al., 2008). Thisreview paper focuses on inkjet-based 3D printing methods(e.g. 3DPTM) only. There is a vast literature on other types of3D printing methods, such as fused deposition modeling(FDM), stereolithography and selective laser sintering.Interested readers are referred to Dimitrov et al. (2006),Espalin et al. (2014), Gibson et al. (2015), Melchels et al.(2010), Murphy and Atala (2014), Sachs et al. (1997), Turnerand Gold (2015), Upcraft and Fletcher (2003) and Yan andGu (1996).

2. Ink characterization: viscosity and surfacetension2.1 Surface tension measurementThe density (!), surface tension (") and the viscosity (#) of thefluids are physical properties that are relevant to inkjetprinting. Surface tension originates from the cohesive forcesexperienced by the molecules at the surface of a liquid. Anumber of techniques can be used to measure the surfacetension of a liquid. A detailed review of each experimentaltechnique is beyond the scope of this paper, and interestedreaders should refer to Adamson (1990). We will onlyhighlight three commonly used methods, namely, Wilhelmyplate, du Noüy ring and pendant drop methods. In theWilhelmy plate method, a plate, usually made ofsurface-treated platinum or paper, is inserted into a fluid ofinterest. As the fluid wets the plate, the plate experiences adownward wetting force. The net force applied on the plate canbe expressed as: F # Wp $ 2(d $ w)$cos%, where F is the forceapplied to the plate, Wp is the weight of the plate, d is thethickness of the plate, w is the width of the plate, $ is the surfacetension of the liquid and % is the contact angle. If the plate iscompletely wetted by the liquid, cos% # 1. By measuring the forceusing a microbalance, the surface tension can be calculated. Inthe du Noüy ring method, a platinum ring instead of a plate issubmerged in the liquid. The ring is attached to a microbalancethat measures the force as the ring is pulled out of the liquid. Theinterfacial tension can be calculated from the following equationF # Wr $ 4&R$, where Wr is the weight of the ring, R is theradius of the ring (inner diameter is assumed to be the same asthe outer diameter because the ring is designed to be thin) and $is the surface tension. In the pendant drop method, a drop isdispensed at the tip of a syringe needle. As drop volumeincreases, the drop shape is progressively distorted from aspherical shape due to gravity. The exact shape of the drop isdescribed by the Bashforth and Adams (1883) equation, which

Figure 2 (a) Basic principles of CIJ; (b) DOD printers (Martin et al.,2008); (c) process diagram of powder-bed based 3D printing, wherea binder is jetted onto a powder bed to create 3D objects (Sachset al., 1993)

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considers the competition between capillary and gravitationalforces. The surface tension of the fluid is calculated by imagingthe drop using a camera and fitting the drop shape (Maze andBurnet, 1971). It is worth noting that Wilhelmy plate and duNoüy ring methods are commonly used to measure theequilibrium surface tension, whereas the pendant drop methodmay be used to measure dynamic surface tension of dropscontaining surface active molecules, for example (Hoath et al.,2012; Morita et al., 2010). However, the time scale associatedwith such method is in excess of 0.01 s, orders of magnitudelarger than that experienced during inkjet printing, which is onthe order of microseconds.

2.2 Rheological characterizationThe apparent shear viscosity of a fluid represents the fluid’sresistance towards flow and is defined as the shear stressdivided by the shear rate. The viscosity of a Newtonian fluid isindependent of the shear rate, but in general the viscosity of afluid may depend on the shear rate applied. Shear-thinningfluids are fluids of which the apparent viscosity decreases asthe shear rate increases. Conversely, shear-thickening fluidsare fluids of which the apparent viscosity increases as the shearrate increases. In inkjet printing, the printing fluid is subjectedto high shear rates, typically in excess of 104 s"1 (Reis et al.,2005), and a short residence time on the order of 5 – 250 's(Hutchings and Martin, 2012). In addition to shear-ratedependence, a fluid may also exhibit viscoelasticity, where thestress is proportional to the strain rate as well as the strain. Forinstance, the addition of colloidal particles and polymers mayresult in elasticity (Hoath et al., 2014; Wagner and Brady,2009).

The viscoelastic response of a fluid depends on thecharacteristic time scale of the process relative to thecharacteristic time scale of the fluid. In piezoelectric-basedinkjet print heads, the printing fluids are subjected tofrequencies on the order of 10-100 kHz (de Jong et al., 2006).Measuring the flow behavior, or rheology, of printing fluids atthese relevant time scale and frequencies is important forcorrelating the basic rheology to their actual behavior duringthe printing process. Commercial torsional rheometers may beused to characterize the basic rheology of the printing fluids;however, the highest accessible shear rates and frequencies arelimited by the motor response and inertia and are typicallyorders of magnitude lower than those relevant to inkjetprinting. Capillary rheometers are capable of measuring thefluid viscosity at high shear rates, but the correspondingresidence time is on the order of milliseconds – much longerthan that experienced by the printing fluid (approximately 10's) (Wang et al., 2012).

As for high-frequency rheology, a custom-built squeeze-flowrheometer, named piezo-axial vibrator (PAV), has beendeveloped by Pechhold et al. at the University of Ulm(Kirschenmann and Pechhold, 2002). The PAV is driven by apiezoelectric element and can access a frequency ranging from1 Hz up to 12 kHz, closer to the characteristic frequenciesrelevant to inkjet printing. Torsional resonators, first explored byMason (1947), are able to achieve to megahertz regime, butmostly limited to a single frequency (Mason, 1947). Wagner andco-workers developed a set of two torsional resonators which

provides access to five discrete frequencies between 3.7 and 57kHz (Fritz et al., 2003).

2.3 Direct imagingGiven the challenges in measuring the rheology at highfrequencies, short residence time and high shear rates, directimaging of the jetting behavior proves to be a morestraightforward method to evaluate the jettability of printingfluids. Both the spatial resolution and temporal resolution ofthe imaging method are important for getting high-quality,sharp images for quantitative analysis. A detailed review onhigh-speed imaging of fluids is published elsewhere (Versluis,2013). A typical imaging platform involves a camera, a lightsource, a print head with control unit and trigger control tosynchronize the jetting and the imaging. The key is to reducethe effective exposure time, which depends on both shutterspeed and the illumination conditions. Small exposure timemay be achieved using a high-speed camera and/or a strobelight source. The shutter speed of the camera and thebrightness of the light source affect the image quality obtainedfrom high-speed cameras.

Although the frame rate of high-speed cameras is typicallyin excess of thousands, the corresponding exposure time is onthe order of milliseconds or less, which is longer than theillumination time of a flash light source on the order ofnanoseconds. Besides, spatial resolution is compromised asthe frame rate increases as the number of frames is limited bythe data transfer speed. Several research groups have appliedhigh-speed and stroboscopic imaging to capture the dropformation in inkjet printing (Dong et al., 2006; Hutching et al.,2007). For instance, Hutching et al. (2007) used a high-speedcamera with a “spark flash” light source with an intense 20-nsillumination to reduce the image blurring of drops traveling ata speed of 5 to 20 m/s. Figure 3 compares the image collectedusing the spark flash technique with that captured with anordinary strobe light. Technological advances in LED lighting

Figure 3 Images of a UV-curable ink jetted into air captured using:(a) a standard strobe illumination with longer illumination time ((1's); and (b) a “spark flash” technique with 20-ns flash illumination(Hutching et al., 2007)

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have enabled the development of inkjet imaging platforms at arelatively low cost. Further, Bognet et al. (2016) developed aninkjet fluid testing platform using inexpensive sound card,instead of a lock-in amplifier, to synchronize the jet actuationand imaging with a time precision of 5 's.

2.4 Dynamic measurementsDynamic surface tension and viscosity data may be obtainedby directly imaging and recording the oscillations of afree-flight drop. In general, Newtonian fluids follow a “freeshape” mode, where the restoration of drop shape anddamping of oscillations are due to the surface tension andviscosity (Lamb, 1895). Recent studies suggested that suchanalysis may be extended to complex fluids. Yang et al.reported dynamic surface tension data for drops with a volumein the pL to 'L range and for an experimental time scale of10"5 to 10"2 s. In this work, drop oscillating method wasfirst validated by using hydroxyethyl cellulose aqueoussolutions and further applied to aqueous poly(3,4-ethylenedioxythiophene) polystyrene sulfonate(PEDOT:PSS) solutions and colloidal suspensions, whichare shear thinning (Yang et al., 2014). Hoath et al. studiedoscillating drops of aqueous solutions containing PEDOT:PSS, which exhibited shear-thinning behavior. Theviscosity of PEDOT:PSS solution first decreased as thedroplet exited the nozzle due to high shear, but the viscositysubsequently increased as the drop detached from thenozzle. Additionally, the dynamic surface tension valueswere also found to be 1.5 to 2 times higher than theequilibrium values because of the finite time scale(approximately 4 ms) for the surface active molecules todiffuse from the bulk to the interface (Hoath et al., 2015).The free-flight drop analysis offers important access to fluidproperties at a time scale that is relevant to inkjet printing.

3. Jet breakup and drop formationThe jet breakup and drop formation during inkjet printingdepends on the interplay between inertial, viscous, elastic andsurface forces. Table II summarizes the dimensionlessnumbers that are useful for understanding the jetting behaviorand identifying the printable region [Figure 4(a)]. Themagnitude of dimensionless numbers indicates the relativeimportance of different forces and time scales at play, as

described in greater detail in Table II. For a simple Newtonianfluid where the viscosity is independent of the shear rate andthere is no elasticity, the Ohnesorge number can be used todetermine a range in which printing is possible. Derby (2010,2011) found that if the Oh number is too large (!1), the fluidis so viscous that there is not sufficient energy to form a jet andthat if the Oh number is too small (%0.1), surface tension willinduce satellite drop formation. The Oh number of theprintable region is estimated to be between 0.1 and 1, asillustrated in Figure 4(a). For fluid mixtures of ethanol, waterand ethylene glycol, the printable region was determinedexperimentally to be between an Oh-value of 0.07 to 0.25(Jang et al., 2009).

While calculating the Oh number may be useful, theprediction of the printable region is based on a simple Newtonianfluid. Additional dimensionless groups, such as the Weissenberg(Wi) number and Deborah (De) number, are needed fordescribing the behavior of viscoelastic fluids. The product of Wiand De numbers results in a dimensionless “Elasticity number”(El), which describes the relative importance of the inertia andelastic stresses (McKinley, 2005). The proper use of Wi and Denumbers requires correctly identifying the characteristic time ofthe fluid, the characteristic time of the deformation and the timeof observation. Identifying a single, appropriate characteristictime for the fluid is challenging in practice because most complexfluids have multiple relaxation times. In such cases, thecharacteristic time of the fluid is taken as either the first momentof the relaxation times or the longest relaxation time (Dealy,2010). Clasen et al. (2012) studied the dispensing of modelNewtonian, shear thinning and viscoelastic fluids anddemonstrated how different dimensionless groups can bepractically used to map out an operating space for dispensingcomplex fluids. They observed that material-property-baseddimensionless groups (Oh, De and Ec) define which mechanism(inertial, viscosity and elasticity) dominates the initial filamentthinning process, whereas dynamic (i.e. jet-velocity-dependent)dimensionless groups (Ca, We and Wi) determine the dominantmechanism (dripping vs jetting) during the subsequent thinning[Figure 4(b)]. The authors put forward several theoreticaltransition values. For instance, if Oh ! 0.2077, viscous effectsdominate inertia, and if Ec ! 4.7015, elastic effects dominateviscous effects. Likewise, if De ! 0.9766, elastic effects dominateinertia. The six dimensionless groups are interrelated. A set of

Table II Typical dimensionless groups used to describe capillary thinning and jetting of Newtonian and viscoelastic fluids

Dimensionless group Definition Physical meaning

Ohnesorge number Oh # We1/2/Re Relative importance of viscous compared to inertia and surface forcesDeborah number De # )/&!R3/" Ratio between the elastic relaxation time and the time of observation (or the

capillary thinning time scale)Elasto-capillary number Ec # )"/#R Relative importance of elastic and capillary effects compared to viscous effectsWeber number We # !DV2/" Ratio between inertia and surface forcesWeissenberg number Wi # )V/D Ratio between the characteristic relaxation time of the fluid and deformation

rateCapillary number Ca # #V/" Relative importance of viscous forces and surface tensionElasticity number El # Wi/Re # #)/!D2 Relative importance of inertia and elastic forcesReynolds number Re # !DV/# Ratio between inertia and viscous forces

Notes: ! is the density, # is the viscosity, " is the surface tension and ) is the characteristic time of the fluid, whereas D is the characteristic length(usually the nozzle diameter) and V is the velocity of the jet

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two material-property-based dimensionless groups and onedynamic group are required to fully describe a dispensingoperation. Further, the dominant mechanism may change duringthe thinning process. To account for this, the authors proposedto define the dimensionless groups using the time-dependentfilament radius instead (Clasen et al., 2012). In the next section,the current understanding of three different common types ofinks, namely, particle suspensions, viscoelastic fluids andphase-change fluids, will be presented.

4. Common inkjet fluids4.1 Particle suspensionsIn graphic art printing, pigments are used to create colors,where the insoluble pigments are first dispersed in a fluid,forming a suspension. The use of pigment suspensions forinkjet printing can be traced back to 1970s (Buehner et al.,1977). More recently, suspensions containing metal- andcarbon-based particles are used to create conductive patternsand antennas on substrates for electronic applications (Ridaet al., 2009; Singh et al., 2010; Tortorich and Choi, 2013).The stability of the suspension-based inks over time is animportant parameter for ink formulations, as it determines theshelf lives of the inks. Particles may settle due to gravity anddensity difference between the particles and suspendingmedium. The settling velocity may be estimated using theStokes equation:

Vsettle *29

!!p + !f"#

gRp2 (1)

where Vsettle is the settling velocity (m/s), g is the gravityconstant (m/s2), !p and !f are the densities of the particle andthe fluid, respectively (kg/m3), Rp is the radius of the particle(m) and # is the dynamic viscosity (Pa s).

Although equation (1) suggests that the settling velocitydecreases with reducing particle sizes, it does not account forthe increase in the surface energies of the systems associatedwith small particles like nanoparticles, which will likely lead toparticle aggregation and consequently sedimentation andprobable nozzle clogging. In such cases, polymers and/orsurfactants are usually added to stabilize the suspension byinducing electrostatic interactions and steric hindrance. As a

rule of thumb, the effective size of the particles should be 20to 50 times less than the nozzle diameter to avoid clogging(Hutchings and Martin, 2012). For particles with a hightendency to settle, a print head with recirculation may be usedto keep the particles suspended (Riegger et al., 2014).

4.1.1 Rheology of particle suspensionsThe rheology of a particle-based ink depends on the loading ofthe particles. Inclusion of particles in a liquid is known toincrease the viscosity of the suspension (Einstein, 1906, 1911;Larson, 1999). However, at low particle concentrations, theink behaves essentially like the suspending medium, as alow-viscosity fluid. Derby (2011) plotted Z (# 1/Oh) valuesbased on the experimental data of ceramic suspensions fromliterature and found that the printable region shows a goodagreement with Reis’s theoretical prediction (1 % Z % 10).Reis et al. (2005) studied concentrated (20 to 40 vol.%)suspensions of fine, dispersant-stabilized alumina particles(0.3 'm) using a piezoelectric drop generator. They observeda linear dependence of both the drop velocity and volume onthe driving voltage and a periodic dependence on the frequencyand pulse period. The authors suggested the periodic behavioris a result of the acoustic properties of the chamber.

Wang et al. (2012) matched the low-shear viscosity of aNewtonian fluid and two particle suspensions. They notedthat achieving consistent jetting is more difficult for theparticle suspensions. As shown in Figure 5(a), the viscosity ofboth particle suspensions decreases as a function of increasingshear rate, termed “shear thinning”. For highly concentratedsuspensions, an opposite “shear thickening” effect may occur(Wagner and Brady, 2009). However, such effect is rarelyobserved for suspensions used in inkjet printing, where theparticle loading is typically less than 20 per cent by volume tomaintain a sufficiently low viscosity for printing.

4.1.2 Two-stage breakup processFurbank and Morris (2004) studied the effects of particles ondrop formation using a stroboscopic imaging platform. At lowparticle concentrations with a volume fraction less than 0.1,suspensions showed a pinch-off structure similar to thatexhibited by a pure liquid as the diameter of the liquid threaddecreased due to surface tension. However, particles may betrapped within the liquid thread, leading to the formation of

Figure 4 (a) Printable region identified for simple Newtonian fluids based on the dimensionless Weber number, Reynolds number andOhnesorge number (Derby, 2011). Reprinted with permission from Elsevier; (b) operating space defined by dimensionless groups for dispersingcomplex fluids (Clasen et al., 2012). Reprinted with permission from John Wiley & Sons

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“satellite drops”, as shown in Figure 6(a), for example.Satellite drops are small (micrometer) drops formed as theelongated filament between two adjacent drops undergoesPlateau-Rayleigh instability. At high particle concentrations,the thread formed a “spindle” structure during necking[Figure 6(b)]. The authors observed that increasing theparticle concentration reduced the number of satellite drops,but the drop volumes of any satellite drops increased. Theygeneralized the thinning of the liquid thread as a two-stageprocess. Long before the rupture of the liquid thread, theadded particles increased the viscosity and consequentlyslowed down the thinning process. As the point of rupture wasapproached, the thinning became less consistent due to thelocal trapping of particles (Furbank and Morris, 2007).Similar observations have been reported by Ma et al. forcarbon nanotube suspensions, where liquid threads containingaggregates of carbon nanotubes tended to break randomly andat an earlier time compared to liquid threads containing nocarbon nanotubes (Ma et al., 2008).

Mcllroy and Harlen presented a two-stage theoretical modelfor the capillary thinning of particle suspensions (McIlroy and

Harlen, 2014). In their model, the thinning of a liquidfilament was delayed initially due to the presence of particlesand an increase in the bulk viscosity. As the diameter of theliquid filament reduced to about five times that of the particlediameter, thinning was accelerated due to fluctuations in localparticle density. More recently, Mathues et al. (2015)suggested four jetting regimes during the capillary thinning ofparticles suspended within a Newtonian fluid. The suspensionwas initially considered as homogeneous viscous fluid(Regime 1) until the filament thinned to a transition radius RT

which corresponded to the onset of the concentrationfluctuation regime (Regime 2). In this regime, the dilutedzones thinned faster due to the local decrease in viscosity. Thefilament further developed into a particle-free section wherethe subsequent breakup followed a filament stretching process(Regime 3). The thinning rate reached maximum at this stagebefore it reached a deceleration regime (Regime 4). InRegime 4, the thinning followed the viscous scaling factor ofthe medium and showed no influence by the presence ofparticles.

Figure 6 (a) The time evolution of a drop containing 5 per cent (v/v) poly(methyl methacrylate) (PMMA) particles suspended in a mixture of 23per cent (w/w) zinc chloride/water solution and UCON 90,000 (polyalkylene glycol; Dow Chemical). The images are not uniformly spaced intime; (b) this shows the drop breakup for 15, 20 and 25 per cent PMMA suspensions, respectively, where the particles may be trapped withinthe liquid thread during necking, forming a spindle-like structure (Furbank and Morris, 2004)

Figure 5 (a) Shear viscosity data of pigment (0, 5.7 and 15 per cent; CAB-O-JET 200®, Cabot Corp.) in a Newtonian liquid mixture of waterand glycerin, measured using a Couette viscometer and a capillary viscometer; (b) time evolution of primary and satellite drop positions for apigment suspension jetted into air based on image analysis (Wang et al., 2012); (c) primary and satellite drop positions as referred to in (b)

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4.2 Shear thinning fluidsShear thinning fluids have been reported to suppress theformation of satellite drops that are generally considered to beundesirable in inkjet printing. Hoath et al. (2012) studied theeffect of shear thinning on satellite drop formation usingPEDOT:PSS solutions. These solutions exhibited a strongshear-thinning behavior (Figure 7). Jetting was possiblebecause the solution experienced high shear rates and shearthinned within the print head. As soon as the drop wasdetached from the nozzle, the shear rate decreased and theviscosity increased, suppressing satellite drop formation.However, for highly shear-thinning fluids, any fluctuations inthe shear rate within the nozzle may also lead to inconsistentjetting as the viscosity becomes highly sensitive to the shearrate. Morrison and Harlen (2011) simulated the jetting ofnon-Newtonian fluids using a Lagrangian finite elementmethod. Their simulation results confirmed that shearthinning suppressed the number of satellite drops.

4.3 Viscoelastic fluidsIn addition to shear-rate-dependent viscosity, inkjet fluids mayexhibit elasticity when they are subjected to deformation. Theelasticity may originate from the Brownian motion of smallparticles and/or the inclusion of polymers that are used tostabilize the particles. The viscoelastic response of the inksdepends on the deformation time scale. In piezoelectric inkjetprinting, the inks typically experience deformations at afrequency on the order of 10 kHz, which is not readilyaccessible using commercial rheometer as discussedpreviously. Vadillo et al. (2011) prepared four polymersolutions using polystyrene (PS) with different molecularweights, ranging from 110 to 488 kg/mol, and differentconcentrations (0-0.5 per cent). These solutions havematching linear viscoelastic data, but displayed significantlydifferent jetting behavior, suggesting the importance ofnon-linear viscoelasticity in inkjet printing. In an earlier paper,the same research group correlated the inkjet printingbehavior with experimental data collected from imaging thethinning process of a liquid filament formed between twopistons (Vadillo et al., 2010). Recent work by Hoath et al.(2012) on a weak elastic polymer solution suggested that the

break-off time delayed significantly as the molecular weight ofthe polymer increased.

4.4 Phase-changing inks and three-dimensionalprintingInkjet printing is effective in creating arbitrary planar patterns,but creating 3D objects proves to be difficult as the ink usuallycontains a substantial amount of solvent, which will eventuallyevaporate, leaving behind only a small amount of solidmaterial (Wang et al., 2008). Further, overprinting layers tocreate 3D structure demands a high degree of depositionprecision. Such challenge can, however, be overcome byselecting a phase-change ink with little or no solvent, wherethe phase change is triggered chemically or thermally. Notableexamples include photo-curable acrylics and wax, whereadditional time scales associated with the chemical reactionand heat transfer are involved. For reactive systems, premixingreactive components before printing may risk clogging theprint head and inconsistent jetting as the reaction progressessoon after the mixing. To overcome this, phase change may beinduced thermally or photochemically after printing. Ifmultiple reactive components are printed onto the substrateseparately, drop positioning and subsequent mixing of dropsare critical. Castrejón-Pita et al. studied the coalescence andmixing of a sessile drop and an incoming drop. No noticeablemixing was observed when the sessile drop and the incomingdrop were comparable in size. Mixing was only achieved whenthe sessile drop was significantly larger than the incoming dropand a vortex ring is generated (Castrejón-Pita et al., 2013).The inkjet printing of reactive materials has been successfullyapplied to pattern polymers, metals, quantum dots,biomaterials, etc. (Delaney et al., 2010; Kim et al., 2013;Kramb et al., 2014; Wang et al., 2008). Fathi and Dickens(2012) studied the drop formation instability of caprolactammixtures and suggested the possibility of building 3Dstructures layer by layer through inkjet printing two reactivecomponents sequentially, followed by polymerization(Figure 8).

3D printing is one of the fastest growing technologies inrecent years, although the original concept of rapidprototyping was conceived much earlier. Certain types of 3D

Figure 7 (a) Shear viscosity data of different concentrations of PEDOT:PSS in water; (b) jetting of 1 per cent (w/w) aqueous PEDOT:PSSsolution and 60 per cent (w/w) glycerol in water, respectively

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printing technology are based on inkjet technology and can betraced back to 1994. Gao and Sonin (1994) from MITdescribed a method for the fabrication of 3D structures byprinting wax microdrops. The wax droplets solidify uponcontacting the substrate maintained at a lower temperature. Itis worth noting that heat transfer is generally faster than masstransfer processes, meaning that there is little or no furthermovement upon deposition. Wax also has the additionaladvantage of offering long-term stability for printing materialscontaining particles. The particles embedded within the waxwill have no mobility until the wax is heated up immediatelyprior to printing. Some 3D printing methods use wax as asupport material which will be removed after the parts arecompleted. Another type of 3D printing methods involvesinkjet printing a binder solution (e.g. gypsum, water andorganic solvents) onto a powder bed to consolidate thepowder. However, using a solvent as the binder tends to createparts with pores, limiting the mechanical and dielectricproperties. To create parts that are relatively pore-free, Wanget al. (2008) inkjet printed a photo-curable resin onto apowder bed instead. The wetting of drops on the powder bedis crucial and will be discussed in the next section.

4.5 Bio-printing3D printing using biological cells as the building blocks opensup new exciting opportunities in regenerative medicine anddrug screening. It also enables the creation of cell culturemodels for studying cellular communications and diseaseprogression (Khetan and Burdick, 2011). Many studiessuggested that although cells may be damaged during theprinting, cell viability is not significantly reduced with specialprecautions (Calvert, 2007; Lorber et al., 2014; Murphy andAtala, 2014; Saunders et al., 2008; Xu et al., 2005). Further,most existing studies on bioprinting focus on the correlationbetween printing conditions and cell viability, and relativelyfew studies directly address how the inclusion of cells impactsthe drop formation process in inkjet printing. Xu et al. studiedthe drop formation of a “bio-ink” suspension containing cellsand sodium alginate (NaAlg) in terms of drop detachmenttime, drop volume, drop velocity and the number of satellitedrops (Figure 9) (Xu et al., 2014). It was observed that as thecell concentration increased, the droplet size and velocitydecreased, whereas the breakup time became longer withfewer or no satellite drops.

5. Drop impact, footprint and resolution5.1 Contact angleIn inkjet printing, the final footprint, or contact diameter, of adrop upon deposition onto a substrate is determined by thein-flight drop diameter (d0) as well as the contact angle – theangle between the liquid/vapor interface and the solidsubstrate. The drop footprint in turn determines the spatialresolution of the inkjet printing. If in-flight solvent evaporationis neglected, the final footprint (dcon) of the drop can beestimated from mass balance (Derby, 2010):

dcon * d03# 8

tan !%eqm/2"!3 , tan2!%eqm/2")(2)

where %eqm is the equilibrium contact angle.Equation (2) predicts that a 1-picoliter droplet will give a

final “footprint” of ca. 30 'm for a contact angle of 10°. Toobtain a footprint smaller than the in-flight drop size,equation (2) estimates that an equilibrium contact angle largerthan approximately 110° is needed. Such simple calculationsoffer a rough guidance on the type of contact angle required,but clearly do not consider the surface roughness or porosityof the substrate; the rheology and dynamics involved (e.g.

Figure 8 Proposed method of creating nylon on a substrate by inkjet printing Mixture A (caprolactam and the catalyst) followed by Mixture B(caprolactam and a catalyst activator). The mixture of A and B was then heated by radiation to form nylon (Fathi and Dickens, 2012)

Figure 9 Schematic diagram of an experimental setup for inkjetprinting a “bioink” – an aqueous suspension of cells and NaAlg.The inset figures show the excitation waveform and the dropformation of a bioink containing 1 ' 107 cells/ml (Xu et al., 2014)

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bouncing of the drops after initial impact); and possible“coffee-ring” effect, where the higher solvent evaporation rateat the edge of the droplet leads to particle deposition at theedge, pinning down the contact line (Deegan et al., 1997). Ingeneral, a number of events, such as capillary spreading,retraction and oscillation, usually occur before thesolidification of the droplet. In addition to the previouslydiscussed Re, We and Oh numbers, the dynamic advancingand receding contact angles are also important, as they arerelated to the spreading and recoiling of the drop upon impact.Hsiao et al. (2014) reported that the maximum drop spreadingradii were significantly underestimated without consideringthe impact initial. The drop impact on relatively smooth andflat surfaces has been intensely studied by Derby (2010), andan excellent review on this topic has been given by Yarin(2006). The interactions between multiple drops during thedeposition of inkjet printing has been explored usingsimulation (Zhou et al., 2015). Industrial-scale inkjet printerstypically produce a line-width of 20 'm or larger, althoughsmaller features [down to ( 100 nm (Sele et al., 2005)] havebeen obtained via electrohydrodynamic printing, which usesan electric field to stretch the fluid (Park et al., 2007),modifying the surface topology (Hendriks et al., 2008) andcreating a surface-energy pattern on the substrate (Sirringhauset al., 2000; Wang et al., 2004).

5.2 Drop impact on rough surfacesThe apparent contact angle of a drop on the substrate dependsnot only on the chemical composition but also on the topologyor surface roughness. The latter also forms the workingprinciple for creating superhydrophobic surfaces (Roach et al.,2008). In this review paper, we focus on the currentunderstanding of drop impact on both porous and roughsurfaces, such as those found in textiles and powder beds thatare of relevance to creating conformable, stretchableelectronics and 3D objects.

5.2.1 Drop impact on powder and three-dimensional printedstructuresIn powder-bed 3D printing, small drops (approximately 30pl) are first generated from a binder solution. These dropsthen impact the powder layer at a speed on the order of 5m/s, resulting in a crater-like structure upon impact.Increasing the drop velocity is desirable for increasing theproduction rate, but it also increases the impact diameter,reducing the spatial resolution. There is also a competitionbetween the drop spreading on the surface and infiltrationinto the porous bed. The latter is driven by capillary forcesas a result of the voids between the powder particles. Toreduce powder movement upon high-velocity drop impact,a small amount of moisture may be introduced to hold thepowder in place through capillary forces (Sachs et al.,1993). Alternatively, the powder bed may be prepared byfirst spreading the powder as a wet paste, then dried to forma denser powder bed, before a binder is inkjet printed ontothe bed (Grau, 1998).

Holman et al. (2002) studied drops that are relevant toinkjet printing and found that the infiltration time is on theorder of 100-500 ms, significantly longer than the timeassociated with surface spreading. The authors concluded thatsimple models which do not consider infiltration are suffice to

calculate the drop spreading even in the case of poroussurfaces. Zhou et al. studied inkjet printing of conductivetraces onto 3D printed structures created by FDM to produceembedded electronics. Their studies suggested the irregularsurface of the 3D printed substrate led to discontinuity of theinkjet printed pattern and consequently poor conductivity. Toimprove the continuity of the inkjet printed tracks, theyexplored two methods: by applying heat and pressure to“iron” the surface and by using a heated metal tip to “plow”a channel to contain the ink (Zhou et al., 2016).

5.2.2 Drop impact on textile surfacesThe physics of printing on textiles is rather complex becauseof the inherent multi-scale morphology, ranging from thefilaments, yarns and weaves, to folds and wrinkles. Themicrostructure of non-woven textiles is rather similar topapers consists of cellulose fibers. Karaguzel et al. studied thejetting of microdroplets (approximately 90 'm in diameter) onnonwoven fabrics. They found that the spreading andpenetration of droplets depended on the solid volume fraction(SVF) of the substrate (Karaguzel et al., 2008). In the case oflow-SVF, the spreading was determined by the local spacingand fiber orientation because fiber–fiber distance is muchlarger than the drop diameter. For high-SVF, the spreadingand penetration of drops are more dependent on thehydrophilicity of the fiber.

More recently, Park et al. (2006) systematically studied thecorrelations between different types of woven structures andthe corresponding drop spreading. They observed that theprinting qualities (line width, edge sharpness, etc.) dependedon the fabric structural parameters, surface chemistry and theink. As shown in Figure 10, when the print direction is parallelto the warp direction, wicking occurs perpendicular to theprint direction, increasing the actual line width andconsequently lowering the print resolution. Conversely, theactual line width is closer to the minimum or target line widthwhen the print direction is perpendicular to the warpdirection. Several studies pointed out that drop splashing onrough surface becomes more prominent as the ratio of surfaceroughness to the drop size increases (Shakeri and Chandra,2002; Šikalo et al., 2005; Sivakumar et al., 2005). Parallelgrove structures have been created by Kannan and Sivakumarand used as a model system to understand drop impact onnon-flat surfaces. The authors concluded that although bothdrop impact and retraction are influenced by the “surfaceroughness”, flatness of the surface has a more pronouncedeffect on retraction (Kannan and Sivakumar, 2008). There area few theoretical studies attempted to correlate the surfaceroughness with drop spreading and retraction (Bussmannet al., 2000; Kim and Chun, 2001; Roisman et al., 2002).

6. Summary and future outlookInkjet printing is a versatile technique capable of patterninga wide range of materials, including polymers, metals,ceramics and biomaterials. Drop formation in inkjetprinting is governed by the interplay between the viscous,elastic and surface forces. The complexity of the inkjetprinting lies in the multiple time scales and length scalesinvolved. Inkjet printing is characterized by its high shearrates (! 104 s"1), short residence times (5-250 's) and high

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frequencies (10-100 kHz). Jettability of Newtonian fluidshas been well-studied and documented in terms of thedimensionless Ohnesorge number (Eggers and Villermaux,2008). However, inkjet fluids may exhibit non-Newtonianbehavior such as a shear-rate-dependent viscosity andviscoelasticity. In the case of inkjet printing particlesuspensions, the continuum assumption breaks down as thediameter of the liquid thread decreases and becomescomparable to the size of the particles. Direct imaging ofthe jetting process has improved greatly with latesttechnological advances in high-speed and stroboscopicimaging. However, linking the jetting behavior withviscoelasticity requires assessing the rheology at highfrequencies that are relevant to the inkjet printing – ordersof magnitude higher than the frequency accessible bycommercial rheometers. For viscoelastic fluids, additionaldimensionless groups, including the Weissenberg andDeborah numbers, are used to compare the characteristictime scale of the fluid relative to the deformation time scaleand time of observation. In cases where a phase-change orreactive material is used, additional time scales associatedwith the heat transfer and reaction also need to beconsidered. For biological samples, survival rate andviability of cells during and after printing are equally

important to drop placement accuracy and consistency.The resolution of inkjet printing depends on the dropfootprint, which is rather well-established for flat andnon-porous surfaces. For applications such as electronictextiles and 3D printing, understanding drop spreading andpenetration on powder beds and textiles are important fordetermining the lateral and depth resolution. Based on thefundamental understanding and experimental techniques assummarized in this paper, a number of topics warrant morein-depth experimental and theoretical investigations. First,as we continue to map out the operating space of inkjetprinting, it is crucial to identify universal rheologicalfingerprints that can predict the jettability and jettingconsistency. This will further translate to better qualitycontrol and faster new ink formulation and ultimately allowthe rational design of printing inks based on performance aswell as processability. This will be founded on thedevelopment of new, robust and affordable instrumentscapable of measuring fluid properties in the kHz range.Second, certain flow phenomena, such asdeformation-induced thickening thixotropy, are critical tounderstanding inkjet, but a solid theoretical framework isstill lacking (Mewis and Wagner, 2009). Thixotropy refersto the time dependency of viscosity induced by flow. Suchbehavior has been reported for printing inks, and it can beeasily confused with viscoelastic responses (Ferna=ndezet al., 1998; Liang et al., 1996). Measuring and modelingthixotropy will remain an active area of research. Third,from a practical perspective, latest developments of imagingplatforms (Bognet et al., 2016; Castrejón-Pita et al., 2008)further open up the exciting possibility of optimizing thejetting waveform in terms of the smallest drop size, dropsize distribution and jetting consistency. This will furtherimpact and guide the development of new functional inksand future print head designs. As the material set of inkjetfluids continues to expand, it becomes increasinglyimportant to understand the underlying physics to realizethe full potential of inkjet printing.

ReferencesAdamson, A.W. (1990), Physical Chemistry of Surfaces, 6th ed.,

Wiley, New York, NY.Bashforth, F. and Adams, J.C. (1883), An Attempt to Test the

Theories of Capillary Action by Comparing the Theoretical andMeasured Forms of Drops of Fluid, Cambridge UniversityPress, Cambridge.

Bharathan, J. and Yang, Y. (1998), “Polymer light-emittinglogos processed by ink-jet printing technology”, Proceedingsof SPIE, Vol. 3279 No. 1, pp. 78-86.

Bognet, B., Guo, Y. and Ma, A.W.K. (2016), “Controllingsystem components with a sound card: a versatile inkjetfluid testing platform”, Review of Scientific Instruments,Vol. 87 No. 1, p. 015101.

Buehner, W.L., Hill, J.D., Williams, T.H. and Woods, J.W.(1977), “Application of ink jet technology to a wordprocessing output printer”, IBM Journal of Research andDevelopment, Vol. 21 No. 1, pp. 2-9.

Bussmann, M., Chandra, S. and Mostaghimi, J. (2000),“Modeling the splash of a drop impacting on a solidsurface”, Physics Fluids, Vol. 12 No. 12, p. 3121.

Figure 10 (a) and (b): schematic diagrams illustrating therelationship between the actual line width and the printing directionwith respect to the structure of a woven polyester fabric. In case(a), the line is printed in the warp direction, whereas in case (b),the line is printed along the filling direction. (c) and (d) are thecorresponding optical micrographs of the printed lines, showing thatthe actual line width in case (b) is closer to the target, or minimum,line width than that in case (a) (Park et al., 2006)

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Calvert, P. (2007), “Materials science: printing cells”, Science(New York, NY), Vol. 318 No. 2007, pp. 208-209.

Cappi, B., Özkol, E., Ebert, J. and Telle, R. (2008), “Directinkjet printing of Si3N4: characterization of ink, greenbodies and microstructure”, Journal of the European CeramicSociety, Vol. 28 No. 13, pp. 2625-2628.

Castrejón-Pita, J.R., Martin, G.D., Hoath, S.D. andHutchings, I.M. (2008), “A simple large-scale dropletgenerator for studies of inkjet printing”, Review of ScientificInstruments, Vol. 79 No. 7, pp. 0-8.

Castrejón-Pita, J.R., Kubiak, K.J., Castrejón-Pita, A.A.,Wilson, M.C.T. and Hutchings, I.M. (2013), “Mixing andinternal dynamics of droplets impacting and coalescing on asolid surface”, Physical Review E - Statistical, Nonlinear, andSoft Matter Physics, Vol. 88 No. 2, pp. 1-11.

Chen, H.Y., Hou, J., Zhang, S., Liang, Y., Yang, G., Yang,Y., Yu, L., Wu, Y. and Li, G. (2009), “Polymer solar cellswith enhanced open-circuit voltage and efficiency”, NaturePhotonics, Nature Publishing Group, London, Vol. 3,pp. 649-653.

Clasen, C., Phillips, P.M., Palangetic, L. Vermant, J. (2012),“Dispensing of rheologically complex fluids: the map ofmisery”, AIChE Journal, Vol. 58 No. 10, pp. 3242-3255.

Crowley, K., O’Malley, E., Morrin, A., Smyth, M.R. andKillard, A.J. (2008), “An aqueous ammonia sensor basedon an inkjet-printed polyaniline nanoparticle-modifiedelectrode”, The Analyst, Vol. 133 No. 3, pp. 391-399.

de Jong, J., Jeurissen, R., Borel, H., van den Berg, M.,Wijshoff, H., Reinten, H., Versluis, M., Prosperetti, A. andLohse, D. (2006), “Entrapped air bubbles in piezo-driveninkjet printing: their effect on the droplet velocity”, Physicsof Fluids, Vol. 18 No. 12, pp. 1-7.

Dealy, J.M. (2010), “Weissenberg and Deborah numbers -their definition and use”, Bulletin of the Society of Rheology,Vol. 79 No. 2, pp. 14-18.

Deegan, R.D., Bakajin, O., Dupont, T.F., Huber, G., Nagel,S.R. and Witten, T.A. (1997), “Capillary flow as the causeof ring stains from dried liquid drops”, Nature, Vol. 389No. 6653, pp. 827-829.

Delaney, J.T., Smith, P.J. and Schubert, U.S. (2009), “Inkjetprinting of proteins”, Soft Matter, Vol. 5, p. 4866.

Delaney, J.T., Liberski, A.R., Perelaer, J. and Schubert, U.S.(2010), “Reactive inkjet printing of calcium alginatehydrogel porogens – a new strategy to open-pore structuredmatrices with controlled geometry”, Soft Matter, Vol. 6,p. 866.

Derby, B. (2010), “Inkjet printing of functional and structuralmaterials: fluid property requirements, feature stability, andresolution”, Annual Review of Materials Research, Vol. 40No. 1, pp. 395-414.

Derby, B. (2011), “Inkjet printing ceramics: from drops tosolid”, Journal of the European Ceramic Society, Vol. 31No. 14, pp. 2543-2550.

Dimitrov, D., Schreve, K. and Beer, N. De. (2006),“Advances in three dimensional printing - state of the artand future perspectives”, Rapid Prototyping Journal, Vol. 12No. 3, pp. 136-147.

Dong, H., Carr, W.W. and Morris, J.F. (2006), “Visualizationof drop-on-demand inkjet: drop formation and deposition”,Review of Scientific Instruments, Vol. 77 No. 8, p. 085101.

Dua, V., Surwade, S.P., Ammu, S., Agnihotra, S.R., Jain, S.,Roberts, K.E., Park, S., Ruoff, R.S. and Manohar, S.K.(2010), “All-organic vapor sensor using inkjet-printedreduced graphene oxide”, Angewandte Chemie - InternationalEdition, Vol. 49 No. 12, pp. 2154-2157.

Eggers, J. and Villermaux, E. (2008), “Physics of liquid jets”,Reports on Progress in Physics, Vol. 71 No. 3, p. 036601.

Einstein, A. (1906), “A new determination of moleculardimensions”, Annals of Physics, Vol. 19, pp. 371-381.

Einstein, A. (1911), “A new determination of moleculardimensions”, Annalen Der Physik, Vol. 34, pp. 591-592.

Elmqvist, R. (1951), “Measuring instrument of the recordingtype”, US patent, 2566443.

Espalin, D., Alberto Ramirez, J., Medina, F., Johnson, W.M.,Rowell, M., Deason, B. and Eubanks, M. (2014), “A reviewof melt extrusion additive manufacturing processes: I,process design and modeling”, Rapid Prototyping JournalRapid Prototyping Journal Rapid Prototyping Journal Iss RapidPrototyping Journal, Vol. 20 No. 3, pp. 192-204.

Fathi, S. and Dickens, P. (2012), “Nozzle wetting andinstabilities during droplet formation of molten nylonmaterials in an inkjet print head”, Journal of ManufacturingScience and Engineering, Vol. 134 No. 4, p. 041008.

Fernández, M., Munõz, M.E., Santamaría, A., Azaldegui, R.,Díez, R. and Peláez, M. (1998), “Rheological analysis ofhighly pigmented inks: Flocculation at high temperatures”,Journal of Rheology, Vol. 42 No. 2, p. 239.

Fritz, G., Pechhold, W., Willenbacher, N. and Wagner, N.J.(2003), “Characterizing complex fluids with high frequencyrheology using torsional resonators at multiple frequencies”,Journal of Rheology, Vol. 47 No. 2, pp. 303-319.

Furbank, R.J. and Morris, J.F. (2004), “An experimentalstudy of particle effects on drop formation”, Physics ofFluids, Vol. 16 No. 5, pp. 1777-1790.

Furbank, R.J. and Morris, J.F. (2007), “Pendant drop threaddynamics of particle-laden liquids”, International Journal ofMultiphase Flow, Vol. 33 No. 4, pp. 448-468.

Gao, F. and Sonin, A.A. (1994), “Precise deposition ofmolten microdrops: the physics of digital microfabrication”,Proceedings of the Royal Society A: Mathematical, Physical andEngineering Sciences, Vol. 444 No. 1922, pp. 533-554.

Gelbart, W.M. and Ben-Shaul, A. (1996), “The ‘New’ scienceof ‘complex fluids’”, The Journal of Physical Chemistry,Vol. 100 No. 31, pp. 13169-13189.

Gibson, I., Rosen, D. and Stucker, B. (2015), AdditiveManufacturing Technologies, Springer, New York, NewYork, NY, available at: http://doi.org/10.1007/978-1-4939-2113-3

Grau, J.E. (1998), Fabrication of Engineered CeramicComponents by the Slurry-Based Three Dimensional PrintingProcess, MA Institute of Technology, MA.

Hendriks, C.E., Smith, P.J., Perelaer, J., Van Den Berg,A.M.J. and Schubert, U.S. (2008), “‘Invisible’ silver tracksproduced by combining hot-embossing and inkjetprinting”, Advanced Functional Materials, Vol. 18 No. 7,pp. 1031-1038.

Hoath, S.D., Jung, S., Hsiao, W.K. and Hutchings, I.M.(2012), “How PEDOT:PSS solutions produce satellite-freeinkjets”, Organic Electronics, Vol. 13 No. 12, pp. 3259-3262.

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Hoath, S.D., Vadillo, D.C., Harlen, O.G., McIlroy, C.,Morrison, N.F., Hsiao, W.K., Tuladhar, T.R., Jung, S.,Martin, G.D. and Hutchings, I.M. (2014), “Inkjetprinting of weakly elastic polymer solutions”, Journal ofNon-Newtonian Fluid Mechanics, Vol. 205, pp. 1-10.

Hoath, S.D., Hsiao, W.K., Martin, G.D., Jung, S., Butler,S.A., Morrison, N.F., Harlen, O.G., Yang, L.S., Baine,C.D. and Hutchings, I.M. (2015), “Oscillations ofaqueous PEDOT:PSS fluid droplets and the properties ofcomplex fluids in drop-on-demand inkjet printing”,Journal of Non-Newtonian Fluid Mechanics, Vol. 223,pp. 28-36.

Holman, R.K., Cima, M.J., Uhland, S.A. and Sachs, E.(2002), “Spreading and infiltration of inkjet-printedpolymer solution droplets on a porous substrate”, Journal ofColloid and Interface Science, Vol. 249 No. 2, pp. 432-440.

Hsiao, W.K., Martin, G.D. and Hutchings, I.M. (2014),“Printing stable liquid tracks on a surface with finitereceding contact angle”, Langmuir, Vol. 30 No. 41,pp. 12447-12455.

Hutching, I.M., Martin, G.D. and Hoath, S.D. (2007), “Highspeed imaging and analysis of jet and drop formation”,Journal of Imaging Science and Technology, Vol. 51 No. 5,pp. 438-444.

Hutchings, I.M. and Martin, G.D. (2012), Inkjet Technologyfor Digital Fabrication, Wiley, Chicester.

Jang, D., Kim, D. and Moon, J. (2009), “Influence of fluidphysical properties on ink-jet printability”, Langmuir,Vol. 25 No. 5, pp. 2629-2635.

Kannan, R. and Sivakumar, D. (2008), “Impact of liquiddrops on a rough surface comprising microgrooves”,Experiments in Fluids, Vol. 44 No. 6, pp. 927-938.

Karaguzel, B., Tafreshi, H.V. and Pourdeyhimi, B. (2008),“Potentials and challenges in jetting microdroplets ontononwoven fabrics”, Journal of the Textile Institute, Vol. 99No. 6, pp. 581-589.

Katstra, W., Palazzolo, R., Rowe, C., Giritlioglu, B., Teung,P. and Cima, M. (2000), “Oral dosage forms fabricated bythree dimensional printingTM”, Journal of Controlled Release,Vol. 66 No. 1, pp. 1-9.

Khetan, S. and Burdick, J.A. (2011), “Patterning hydrogels inthree dimensions towards controlling cellular interactions”,Soft Matter, Vol. 7 No. 3, p. 830.

Kim, H.Y. and Chun, J.H. (2001), “The recoiling of liquiddroplets upon collision with solid surfaces”, Physics ofFluids, Vol. 13 No. 3, pp. 643-659.

Kim, K., Ahn, S. II and Choi, K.C. (2013), “Directfabrication of copper patterns by reactive inkjet printing”,Current Applied Physics, Vol. 13 No. 9, pp. 1870-1873.

Kirschenmann, L. and Pechhold, W. (2002), “PiezoelectricRotary Vibrator (PRV) – a new oscillating rheometer forlinear viscoelasticity”, Rheologica Acta, Vol. 41 No. 4,pp. 362-368.

Kramb, R.C., Buskohl, P.R., Slone, C., Smith, M.L. andVaia, R.A. (2014), “Autonomic composite hydrogels byreactive printing: materials and oscillatory response”, SoftMatter, Vol. 10 No. 9, pp. 1329-1336.

Lamb, H. (1895), Hydrodynamics, University Press,Cambridge.

Larson, R.G. (1999), The Structure and Rheology of ComplexFluids, Oxford University Press, New York, NY.

Lean, M.H. (2002), “Method and aparatus for reducing dropplacement error in printers”, US patent 6367909 B1.

Leoni, N.J. and Gila, O. (2013), “Inkjet printhead andprinting system with boundary layer control”, US patent,8596742 B2.

Liang, T.X., Sun, W.Z., Wang, L.D., Wang, Y.H. and Li,H.D. (1996), “Effect of surface energies on screen printingresolution”, IEEE Transactions on Components, Packaging,and Manufacturing Technology: Part B, Vol. 19 No. 2,pp. 423-426.

Lorber, B., Hsiao, W.K., Hutchings, I.M. and Martin, K.R.(2014), “Adult rat retinal ganglion cells and glia can beprinted by piezoelectric inkjet printing”, Biofabrication,Vol. 6 No. 1, p. 015001.

McIlroy, C. and Harlen, O.G. (2014), “Modelling capillarybreak-up of particulate suspensions”, Physics of Fluids,Vol. 26 No. 3, p. 033101.

McKinley, G. (2005), “Dimensionless groups forunderstanding free surface flows of complex fluids”, Bulletinof the Society of Rheology, Vol. 74 No. 2, pp. 6-9.

Ma, A.W.K., Chinesta, F., Tuladhar, T. and Mackley, M.R.(2008), “Filament stretching of carbon nanotubesuspensions”, Rheologica Acta, Vol. 47 No. 4, pp. 447-457.

Martin, G.D., Hoath, S.D. and Hutchings, I.M. (2008),“Inkjet printing – the physics of manipulating liquid jets anddrops”, Journal of Physics: Conference Series, Vol. 105 No. 1,p. 012001.

Mason, W.P. (1947), “Measurement of the viscosity andshear elasticity of liquids by means of a torsionally vibratingcrystal”, Transactions Of ASME, Vol. 68, pp. 359-370.

Mathues, W., McIlroy, C., Harlen, O.G. and Clasen, C.(2015), “Capillary breakup of suspensions near pinch-off”,Physics of Fluids, Vol. 27 No. 9, p. 093301.

Maze, C.C. and Burnet, G. (1971), “Modification of anon-linear regression technique used to calculate surfacetension from sessile drops”, Surface Science, Vol. 24 No. 1,pp. 335-342.

Melchels, F.P.W., Feijen, J. and Grijpma, D.W. (2010), “Areview on stereolithography and its applications inbiomedical engineering”, Biomaterials, Vol. 31 No. 24,pp. 6121-6130.

Mewis, J. and Wagner, N.J. (2009), “Thixotropy”, Advancesin Colloid and Interface Science, Vols 147/148 No. 3,pp. 214-227.

Morita, N., Hirakata, S. and Hamazaki, T. (2010), “Studyon vibration behavior of jetted ink droplets and nozzleclogging”, NIHON GAZO GAKKAISHI (Journal of theImaging Society of Japan), Vol. 49 No. 1, pp. 14-19.

Morrison, N.F. and Harlen, O.G. (2011), “Inkjet printing ofnon-Newtonian fluids”, Proceedings 27th InternationalConference on Digital Printing Technologies, Minneapolis,pp. 360-364.

Murphy, S.V. and Atala, A. (2014), “3D bioprinting of tissuesand organs”, Nature Biotechnology, Vol. 32 No. 8,pp. 773-785.

Okamoto, T., Suzuki, T. and Yamamoto, N. (2000),“Microarray fabrication with covalent attachment of DNA

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using bubble jet technology”, Nature Biotechnology, Vol. 18No. 4, pp. 438-441.

Park, H., Carr, W.W., Ok, H. and Park, S. (2006), “Imagequality of inkjet printing on polyester fabrics”, TextileResearch Journal, Vol. 76 No. 9, pp. 720-728.

Park, J.U., Hardy, M., Kang, S.J., Barton, K., Mukhopadhyay,D.K., Lee, C.Y., Strano, M.S., Alleyne, A.G., Georgiadis,J.G., Ferreira, P.M. and Rogers, J.A. (2007), “High-resolutionelectrohydrodynamic jet printing”, Nature Materials, Vol. 6,pp. 782-789.

Perelaer, J., De Gans, B.J. and Schubert, U.S. (2006),“Ink-jet printing and microwave sintering of conductivesilver tracks”, Advanced Materials, Vol. 18 No. 16,pp. 2101-2104.

Reis, N., Ainsley, C. and Derby, B. (2005), “Ink-jet deliveryof particle suspensions by piezoelectric droplet ejectors”,Journal of Applied Physics, Vol. 97 No. 9, p. 094903.

Rida, A., Yang, L., Vyas, R. and Tentzeris, M.M. (2009),“Conductive inkjet-printed antennas on flexible low-costpaper-based substrates for RFID and WSN applications”,IEEE Antennas and Propagation Magazine, Vol. 51 No. 3,pp. 13-23.

Riegger, L., Ernst, A. and Koltay, P. (2014), “A dispensingsystem for sedimenting metal microparticle solutions basedon a circulation mixer method”, 2nd International Conferenceon Micro Fluidic Handling Systems, University of Freiburg,Germany, pp. 81-83.

Roach, P., Shirtcliffe, N.J. and Newton, M.I. (2008),“Progess in superhydrophobic surface development”, SoftMatter, Vol. 4, p. 224.

Roisman, I.V., Rioboo, R. and Tropea, C. (2002), “Normalimpact of a liquid drop on a dry surface: model forspreading and receding”, Proceedings of the Royal Society A:Mathematical, Physical and Engineering Sciences, Vol. 458No. 2022, pp. 1411-1430.

Rowe, C., Katstra, W., Palazzolo, R., Giritlioglu, B., Teung,P. and Cima, M. (2000), “Multimechanism oral dosageforms fabricated by three dimensional printingTM”, Journalof Controlled Release, Vol. 66 No. 1, pp. 11-17.

Sachs, E., Cima, M., Williams, P., Brancazio, D. and Cornie,J. (1992), “Three dimensional printing: rapid tooling andprototypes directly from a CAD model”, Journal ofEngineering for Industry, Vol. 114 No. 4, pp. 481-488.

Sachs, E., Allen, S., Guo, H., Banos, B., Cima, M.J., Serdy, J.and Brancazio, D. (1997), “Progress on tooling by 3Dprinting; conformal cooling, dimensional control, surfacefinish and hardness”, Proceedings of the Eighth Annual SolidFreeform Fabrication Symposium, Austin, pp. 115-124.

Sachs, E., Cima, M., Cornie, J., Brancazio, D., Bredt, J.,Curodeau, A., Fan, T., Khanuja, S., Laude, A., Lee, J. andMichaels, S. (1993), “Three-dimensional printing: thephysics and implications of additive manufacturing”, CIRPAnnals – Manufacturing Technology, Vol. 42 No. 1,pp. 257-260.

Saunders, R.E., Gough, J.E. and Derby, B. (2008), “Deliveryof human fibroblast cells by piezoelectric drop-on-demandinkjet printing”, Biomaterials, Vol. 29 No. 2, pp. 193-203.

Seerden, K., Reis, N., Evans, J., Grant, P., Halloran, J. andDerby, B. (2001), “Ink-jet printing of wax-based alumina

suspensions”, Journal of American Ceramic Society, Vol. 84No. 11, pp. 2514-2520.

Sele, C.W., Von Werne, T., Friend, R.H. and Sirringhaus, H.(2005), “Lithography-free, self-aligned inkjet printing withsub-hundred-nanometer resolution”, Advanced Materials,Vol. 17 No. 8, pp. 997-1001.

Shakeri, S. and Chandra, S. (2002), “Splashing of molten tindroplets on a rough steel surface”, International Journal ofHeat and Mass Transfer, Vol. 45 No. 23, pp. 4561-4575.

Shimoda, T., Morii, K., Seki, S. and Kiguchi, H. (2003),“Inkjet printing of light-emitting polymer displays”, MRSBulletin, Vol. 28 No. 11, pp. 821-827.

Šikalo, Š., Wilhelm, H.D., Roisman, I.V., Jakirlic, S. andTropea, C. (2005), “Dynamic contact angle of spreadingdroplets: experiments and simulations”, Physics of Fluids,Vol. 17 No. 6, pp. 1-13.

Singh, M., Haverinen, H.M., Dhagat, P. and Jabbour, G.E.(2010), “Inkjet printing-process and its applications”,Advanced Materials, Vol. 22 No. 6, pp. 673-685.

Sirringhaus, H., Kawas, T., Friend, R.H., Shimoda, T.,Inbasekaran, M., Wu, W. and Woo, E.P. (2000),“High-resolution inkjet printing of all-polymer transistorcircuits”, Science, Vol. 290, pp. 2123-2126.

Sivakumar, D., Katagiri, K., Sato, T. and Nishiyama, H. (2005),“Spreading behavior of an impacting drop on a structuredrough surface”, Physics of Fluids, Vol. 17 No. 10, pp. 1-11.

Sweet, R.G. (1965), “High frequency recording withelectrostatically deflected ink jets”, Review of ScientificInstruments, Vol. 36 No. 2, pp. 131-136.

Sweet, R.G. (1975), “Fluid droplet recorder”, US Patent3596275.

Tortorich, R. and Choi, J.W. (2013), “Inkjet printing ofcarbon nanotubes”, Nanomaterials, Vol. 3, pp. 453-468.

Turner, B.N. and Gold, S.A. (2015), “A review of meltextrusion additive manufacturing processes: II, materials,dimensional accuracy, and surface roughness”, RapidPrototyping Journal, Vol. 21 No. 3, pp. 250-261.

Upcraft, S. and Fletcher, R. (2003), “The rapid prototypingtechnologies”, Assembly Automation, Vol. 23 No. 4,pp. 318-330.

Utela, B., Storti, D., Anderson, R. and Ganter, M. (2008),“A review of process development steps for new materialsystems in three dimensional printing (3DP)”, Journal ofManufacturing Processes, Vol. 10 No. 2, pp. 96-104.

Vadillo, D.C., Hoath, S.D., Hsiao, W.K. and Mackley, M.R.(2011), “The effect of inkjet ink composition on rheologyand jetting behaviour”, NIP and Digital Fabrication.

Vadillo, D.C., Tuladhar, T.R., Mulji, A.C., Jung, S., Hoath,S.D. and Mackley, M.R. (2010), “Evaluation of the inkjetfluid’s performance using the ‘Cambridge Trimaster’filament stretch and break-up device”, Journal of Rheology,Vol. 54 No. 2, p. 261.

van den Berg, A.M.J., Smith, P.J., Perelaer, J., Schrof, W.,Koltzenburg, S. and Schubert, U.S. (2007), “Inkjet printing ofpolyurethane colloidal suspensions”, Soft Matter, Vol. 3,p. 238.

Vaught, J.L., Cloutier, F.L., Donald, D.K., Meyer, J.D.,Tacklind, C.A. and Taub, H.H. (1984), “Thermal ink jetprinter”, US patent 4490728.

Inkjet and inkjet-based 3D printingYang Guo, Huseini S. Patanwala, Brice Bognet and Anson W.K. Ma

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201

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Versluis, M. (2013), “High-speed imaging in fluids”,Experiments in Fluids, Vol. 54 No. 2, p. 1458.

von Hasseln, K.W. (2013), “Apparatus and method forproducing a three-dimentional food product”, US Patent0034633 A1.

Wagner, N.J. and Brady, J.F. (2009), “Shear thickening incolloidal dispersions”, Physics Today, Vol. 62 No. 10,pp. 27-32.

Wang, T., Patel, R. and Derby, B. (2008), “Manufacture of3-dimensional objects by reactive inkjet printing”, SoftMatter, Vol. 4, p. 2513.

Wang, X., Carr, W.W., Bucknall, D.G. and Morris, J.F.(2012), “Drop-on-demand drop formation of colloidalsuspensions”, International Journal of Multiphase Flow,Vol. 38 No. 1, pp. 17-26.

Wang, J.Z., Zheng, Z.H., Li, H.W., Huck, W.T.S. andSirringhaus, H. (2004), “Dewetting of conducting polymerinkjet droplets on patterned surfaces”, Nature Materials,Vol. 3 No. 3, pp. 171-176.

Xu, T., Jin, J., Gregory, C., Hickman, J.J. and Boland, T.(2005), “Inkjet printing of viable mammalian cells”,Biomaterials, Vol. 26 No. 1, pp. 93-99.

Xu, C., Zhang, M., Huang, Y., Ogale, A., Fu, J. and Markwald,R.R. (2014), “Study of droplet formation process duringdrop-on-demand inkjetting of living cell-laden bioink”,Langmuir, Vol. 30 No. 30, pp. 9130-9138.

Yan, X. and Gu, P. (1996), “A review of rapid prototypingtechnology and systems”, Computer Aided Design, Vol. 28No. 4, pp. 307-318.

Yang, L., Rida, A., Vyas, R. and Tentzeris, M.M. (2007),“RFID tag and RF structures on a paper substrate usinginkjet-printing technology”, IEEE Transactions on MicrowaveTheory and Techniques, Vol. 55 No. 12, pp. 2894-2901.

Yang, L., Kazmierski, B.K., Hoath, S.D., Jung, S., Hsiao,W.K., Wang, Y., Berson, A., Harlen, O., Kapur, N. andBain, C.D. (2014), “Determination of dynamic surfacetension and viscosity of non-Newtonian fluids from droposcillations”, Physics of Fluids, Vol. 26 No. 11, p. 113103.

Yarin, A.L. (2006), “Drop impact dynamics: splashing,spreading, receding, bouncing. . .”, Annual Review of FluidMechanics, Vol. 38, pp. 159-192.

Zhou, W., List, F.A., Duty, C.E. and Babu, S.S. (2016),“Fabrication of conductive paths on a fused depositionmodeling substrate using inkjet deposition”, RapidPrototyping Journal, Vol. 22 No. 1, pp. 77-86.

Zhou, W., Loney, D., Fedorov, A.G., Degertekin, F.L. andRosen, D.W. (2015), “Shape evolution of multipleinteracting droplets in inkjet deposition”, Rapid PrototypingJournal, Vol. 21 No. 4, pp. 373-385.

Corresponding authorAnson W. K. Ma can be contacted at: anson.ma@uconn.edu

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Inkjet and inkjet-based 3D printingYang Guo, Huseini S. Patanwala, Brice Bognet and Anson W.K. Ma

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